Abrasive wheel and method of manufacture



Patented Oct. 22, 1929 I UNITED STATES PATENT OFFICE HEN-BERT S IMONDS, O1? DAYTON, OHIO, ASSIGNOB TO THE A. A. SIMONDS-DAYTON COMPANY, OF DAYTON, OHIO, A CORPORATION 01 OHIO ABRASIVE WHEEL AND METHOD OF MANUFACTURE No Drawing. Application filed July 1,

This invention relates to an abrasive material, and particularly to abrasive wheels and the like.

The abrasive Wheels now generally used in 5 industry are artificially prepared. Such wheels are generally composed of an abrasive materialheld together by a fused bonding material or binder. When these wheels are used for grinding or abrading o erations, as for example in grinding meta parts, the wheel itself by its use generates disru tive forces,-these forces being generally 0 two kinds, ((1) those resulting from expansion and contraction of the wheel material due to temperature changes during use of the wheel,

and (b) centrifugal forces due torapiderotation of the wheel.

Considerable heat energy is enerated at the zone of contact, as a result'o the friction rial which are present as the generated heat is conducted through the wheel material away from the zone of. heat generation. F urthermore, the instant a given zone of contact moves out of contact with the workthe heat energy impressed upon that zone is rapidly dissipated. As a result, during use of an abrasive wheel the material. of that wheel is subjected to rapidly succeedin temperature shocks; which in turn set up disruptive forces arising from within the wheel itself which tend to destroy the wheel. j. 1

An artificially prepared abrasive wheel consists generally of grains or' articles of abrasive material, held together y a binder. This binder is usually a fused mass which, self contained within the wheel, holds the particles of abrasive material firmly. counteracting the disruptive or disintegrating tend- 1925. Serial No. 40,948.

whole, or of a considerable portion of the wheel, a sufficiently powerful disruptive force is set up to crack 1; 1e wheel the result may be-under the influence of the centrifugal forces setup during rapid rotation of the wheels-complete destruction of the wheel, its

disintegration as a whole.

One of the principal objects of the present invention is to provide an abrasive wheel which is free from the above described defects heretofore inherent in. wheels of this char acter, and a method of making such a wheel.

Another object of the invention is to provide an abrasive wheel composed of such material that it has a negligible coefiicient of ex%ansion,i. e. a coefiicient of expansion insu cient' to cause disruption of the material of the wheel during operation. 7 a f Other objects and advantages of the .inven-' tion will be apparent from the description set out below.

While this invention is enerally applicable to an abrasive body and to the method of making such an'abrasive body it is particularly applicable to ceramic abrasive wheels and for purposes of clearer description, and as setting out a preferred embodiment of the invention, it is described in connection with such a form of abrasive wheel as is generally used in industry.

The granules or particles of abrasive material may be of any suitable character, but in actual practice usually consist of emery, fused silicon carbide, fused aluminum oxide, or any desired mixture of these. These materials are crushed or ground to a desired size, are mixed with a suitable binding material and molded into the proper form. The molded forms are then dried, after which they are placed in a kiln and heated to a temperature sufficiently high to fuse the bonding material,

but not sufficiently high to affect the abradof a mixture of compounds of the so called alkali and alkaline earth groups with certain other compounds such as oxides of silicon and aluminum. As an illustration the clay known commercially as Albany slip, which is often used as one of the constituents of such a binder, has the following general analysis Percent Moisture .052 Ignition loss A 7.970 S10 59.570 A1 0, 11.720 F6 0 5.240 eO .860 P 0 .180 (1:10 6.400 Mg() 3.220 K 0 2.680 Na O .900 MnO .460

,Other constituents used are. silica compounds, such as ball clay, feld-spar, and the like. These have substantially the same compounds as Albany slip" but in different relative proportions. By properly admixing these several materials 'a binder of desired chemical constituency may be secured.

I have found that increasing the relative proportions of alkali compounds tends to increase the rate of fusion of the mass,-that is, the time interval necessary for accomplishing complete fusion at a given temperatureso much so in fact as to often cause objectionable frothing. Also increasing the proportion of alkali compounds tends to increase the coefficient of expansion of the resulting fused binder. The akaline earths I have found tend to lower the coefficient of expansion. They also decrease the rate of fusiongiving a quiet and gradual fusionoften soaffecting the rate of fusion that there is a lack of homogeneity in the fused binder which is very undesirable as it causes strains which greatly increase the destructive effect of temperature shocks.

Heretofore then, it has been the general desire to so proportion these compounds as y to give fluidity and rapid fusion, without frothing. I have found that if compounds of boron are added insuitable quantity the resulting mixture will fuse readily without frothing, will be quite fluid so that homogeneity is attained, and will have a low coefficient of expansion. Furthermore the addition to the bond mixture of the boron increases the temperature range of fusing so that such nicety of control of the temperature within the. oven during manufacture need not be maintained as with bond mixtures heretofore used, without boron.

As stated above bonds are usually made up of mixtures of natural clays, and the like, which contain a large number of various constituents; but these bonding materials may be, for purposes of convenience in description, grouped in three general classes, namely, oxides of the alkali and alkaline earth metals designatedv generally R0; oxides of aluminum and the like designated generally R 0 and a group called generally ,acid which comprise compounds such as SiO The relative proportions of the various groups and of the several members of each group have been generally determined empirically and to make admixing easy the proportions have been set out in terms of numbers of molecules. That is to say the relative quantities desired having been determined they are stated in terms of relative numbers of molecules in each-group, or what is for convenience termed molecular ratios. Thus a fair mixture as heretofore used might be 1 R0 R 0 Acid 1 1 6 which means that there should be used the same number of R 0 molecules as there are used RO molecules, but six times as many acid molecules as there'are RO molecules. And RO includes all of the alkali and alkaline earths.

Of course the relative proportions of the alkali and alkaline earth compounds must also be determined. These again may be determined in the same way. For example the relative proportions may be 9 molecules of alkalies to 1 molecule of alkaline earths. This would give a bond which is readily fusible, but of high coefficient of expansion. The'relative proportions of these two groups of compounds may be considerably varied with respect to each other; but the relation 0": the total RO group to the total of other groups should remain the same.

Now, as stated above, I have found that the addition of boron compounds, particularly boron oxide, or boracic acid, will increase the fusibility, the fluidity of the fusing mass, and will also lower the coefiieient of expansion of the resultant fused binder.

So'that by adding boron compounds the proportion of alkalies relative to alkaline earths in the R0 group may be greatly decreased, and more satisfactoryresults attained. For example, I have. found the following the proportions being in molecule ratios.

Of course, this precise proportion of the' bond constituents is not essential; and may be rather widely departed from and satisfactory results secured. To illustrate, in terms of molecular ratios, the proportions may be varied over a considerable range, as follows:-

R0 mo. Acidmagma Alzoa nabs;

- earths In actual practice very satisfactory results 1 have been obtained where the percentage of boron compound varied from 3% to 10% of the whole quantity of bonding material, by

weight. The most desirable proportion of boron compound will depend upon the rel ative proportions of other constituents'-such for example as th; proportion of alkalies to alkaline earths in the RO groupand as low as 1% of boron compounds by weight will" have appreciable effects while as high as 20% may be used satisfactorily. And the practicing of-this invention gives results heretofore not attained, for, to my knowledge no one has heretofore provided a ceramic abrading wheel in which expansion during use is negligible; which has a substantially negligible coefficient of expansion; either of the wheel as a Whole or of the bondingmateri'al; and which is therefore non-disruptive;

Such a bond is able to withstand temperature shocks to a degree hitherto unknown in connection with previously known abradin wheels, and as a result the wheel is much longer lived than previously known wheels. Furthermore such a bond has greater physical strength than other known bonds.- I have made comparative breaking tests on wheels made with the old regular bonds and with the bond shown above, b t using only half as much of the new bond as of the old,

' and have found such new bond wheelsto show greater physical strengthto require a greater force to break themthan the old bond wheels. This is a matter of great practical importance. for the abrading effect of the wheel is due to the particles of abrasive material, the bond merely acting as a holder for this abrasive material. And any increase in the quantity of abrasive material for a g1ven working surface means greater effectiveness and also lon er life.

Such new 0nd, when it'has been fused and cooled, will have a negligiblehcoeflicient of expansion. Andan abrasive wheel in which is used such bonding material will also have a negligible coefiicient of expansion. By

the term negligible as used here, I do not,

necessarily, mean that the bond,.or the wheel as a whole, has a zero coefiicient of expansion; but that the-coeflicient of expansion is relatively so low that the danger of general or local rupture or disintegration of the wheel due to temperature shocks or unequal expansion during use is decreased to a point practically unobjectionable, or even substantially eliminated.

I have also found that, apparently, in its ordinary commercial state boric oxid, boracic acid, borax, or the like, may not be added to the bond to give satisfactory results.

When so added to the bond the resulting wheel when it cools will often disintegrate.

with almost explosive violence. But this ob- 'ectionable behavior will be avoided if the oron compound is first treated to permanently remove its waterof. crystallization or rendered insoluble. One satisfactory and simple method of rendering such compounds suitable for use is to fuse the boron compound with silicavcontaining compound to form a'complex silicate. A suitable proportion of such fused boron compound, proper ly ground, is admixed with a proportional guan'tity of bonding material in the ordinary orm of plastic cla the abrading material being also admixe therewith, after which the wheels are molded to the desired form and then fused to the' finished condition.

' While the abrading material or wheel herein described and the method of making it constitute preferred embodiments of the invention, it is'to be understood that the invention, is not limited thereto, and that changes maybe made therein without de parting 'fronr'the scope of the invention which s defined in the appended claims.

What is claimed is -1. A, ceramic abrasive wheel composed of material which includes an abrasive substance and a bond comprising'compounds of the alkali metals'and of the alkaline earth metals, and boric oxid, said bond constituents being present-in'proportions so controlled that upon fusion into a completed wheel said wheel will have a negligible expansion during use.

2. A ceramic abrasive wheel composed of material which includes an abrasive substance and a bond comprising compounds having the general formula RO, R 0 admixed with compounds designated acid, the. compounds being admixed in the general'ratioof 1: 1:9 when determined in molecular equivalents.

3. A ceramic abrasive wheel composed of material which includes an abrasive substance and a bond comprising compounds having the general formula R0, R 0, admixed with compounds designated acid, the compounds being admixed in the general ratio of 1: 1: 9 when determined in molecular equivalents, the acid compounds comprising boron oxide in the proportion of from .1 to 1.2 in molecular equivalents, of the entire quantity of acid compounds.

.4. A ceramic abrasive wheel composed of material which includes an abrasive substance and a bond comprising from .1.5 of alkaline earth compounds iihd .11.2 of boron compounds, in terms of molecular equivalents,

said bond when fused having a negligible ex-' pansion during use.

5. In the preparation of an abrasive wheel, in which an abrasive material is admixed with a bonding material, and given a predetermined shape after which the shaped wheel is heated in a kiln to fuse the bonding material; the method of preparing bonding material which comprises fusing a boron compound with silica compounds to form complex boron silicate and incorporating the resulting fused mass in the bonding material with the boron present in the bonding material in the proportion of from .1 to 1.2, in terms of molecular equivalents.

6. A ceramic abrasive wheel, which is composed of material which includes an abrasive substance, and a fused ceramic bond compris and a ceramic fused'bond comprising a compound of boron, said compound being present in the. proportion of from 3 to 10% of the total weight of the bond, said bond when fused having negligible expansion during use.

9. A ccramicabrasive wheel composed of an abrasive substance and a bond comprising silica, boron, sodium and aluminum fused together, the constituents of said bond being in proportion so controlled that in the resulting completed wheel the bond has a negligible coeilicient expansion.

10. A ceramic abrasive wheel composed of an abrasive substance and a fused bond, said bond being composed of materials relatively so proportioned that the completed fused wheel will be free from objectionable disruptive forces, the materials of which said bond is composed comprising .5 of alkaline earths and 1.2 of boron oxid in terms of molecular equivalents.

.11. In the preparation of abrasive wheels, in which an abrasive material is admixed with a bonding material comprising as one constituent a substantial proportion of a boron compound; the method which comprises treating the boron compound before its admixture with additional bonding material, to render it insoluble, and admixing such treated boron compound with a preponderance of additional bonding material, the said materials being relatively so proportioned that upon fusion of the bond the completed wheel will be free from objectionable disruptive forces due to expansion and the like.

12. In the preparation of an abrasive wheel, in which an abrasive material is admixed with a bonding material, and given a predetermined shape after which the sha ed wheel is heated to fuse the bonding material; the method which comprises fusing a boron compound with silica compounds to form complex boron silicates, admixing the resulting fused material with a preponderating amount of additional bonding material, incorporating the resulting abrasive material within the admixed bonding materials, subjecting said admixed bonding material and abrasive material to fusion to form an abrasive wheel, the several constituents of said bonding material being so relatively proportioned that upon fusion the resulting completed wheel will have a negligible expansion during use.

13. The method in formation of ceramic abrasive wheels, which comprises admixing abrasive material with a bonding material comprising as constituents thereof oxides of silicon, alkali and alkaline earth metals, and boron with the relative proportions of such oxides so controlled that upon fusion the resultin fused bond during use will have a negligible expansion; forming such admixed abrasive material and bonding material into desired shape; and then fusing the shaped bod 14 The method in the formation of ceramic abrasive wheels, which comprises admixing clay containing oxides of silicon, aluminum, and sodium in controlled proportions, with a previously fused compound of boron, to give a resulting bonding mixture of controlled relative constituents, the proportions of the various named compounds being such that on fusing the bond will have a negligible expansion during use.

15. An abrasive wheel composed of an abrasive material and a fused bond, said bond comprising a fused mixture of a boron compound and clay containing an admixture of oxides of silica, and alkali and alkaline earth metals, the relative proportions of the coilstituents going to make up such said bond being such that upon fusion the resulting fused bond will have a negligible expansion during use.

16. For use as a constituent in the bonding material which goes to make up an artificially prepared abrasive Wheel, and as a composition of matter, a complex boron silicate formed by fusing a boron compound with a silica containing compound, the constituent compounds being so proportioned as to give to the fused complex boron silicate a predetermined eomposltion range adapted to impart to the fused mass a negligible coefiicient of expansion.

In testimony whereof I hereto affix my sig- 11 ature.

HERBERT R. SIMONDS. 

